Hydrophobic behavior of insulators coated with RTV silicone rubber

Room temperature vulcanized (RTV) silicone rubber coatings are applied to electrical insulators to improve their subsequent insulation strength, particularly under wet conditions. Under prolonged wetting the hydrophobicity of the coating is reduced temporarily and the insulator protection is lost. After a dry period, a recovery of the hydrophobicity takes place. To investigate this phenomenon, the surface was subjected to various wetting conditions. Measurements of the contact and the sliding angles were used to determine the state of the surface. The surface free energy of the RTV was calculated as a function of time of exposure of the surface to salt fog.< >